1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle which is able to travel under the driving force from at least one of an engine and a drive motor connected to the engine.
This application is based on Japanese Patent Application No. 2003-292170, the contents of which are incorporated herein by reference.
2. Description of Related Art
Conventionally, for example, there has been a torque fluctuation control unit for suppressing engine torque fluctuation comprising; a power generation unit which applies a counter torque to a crankshaft driven by the engine, and an electrical drive unit which applies a positive torque to the crankshaft. In this unit, during an all cylinders operation or a partial cylinders operation of the engine, then synchronized with periodic fluctuations of torque generated in the respective crankshafts, the power generation unit is operated when the torque is increasing and the electrical drive unit is operated when the torque is decreasing, so that a torque counter to the engine torque fluctuations is applied in order to suppress the engine torque fluctuation. During the partial cylinders operation, by making the operation time of the power generation unit or the electrical drive unit longer than the operation time during the all cylinders operation, the torque fluctuation of the engine may be more strongly suppressed (for example, see Japanese Unexamined Patent Application, First Publication No. Sho. 61-66818).
Incidentally, in a hybrid vehicle which is able to travel under the driving force from at least one of an engine and a drive motor to realize low pollution and high fuel efficiency, there has been a problem in that, if more apparatuses are provided in addition to the apparatus originally necessary for the vehicle to travel, the vehicle becomes complicated, and not only is cost increased but also the vehicle becomes larger than necessary, causing a deterioration in fuel consumption efficiency. Therefore, in a hybrid vehicle, by not providing the power generation unit and the electrical drive unit as in the conventional technology, but using a drive motor connected to the engine, instead of the power generation unit and the electrical drive unit, a damping control which generates the torque for suppressing the engine torque vibration is executed in the drive motor.
However, if the damping control is executed by the drive motor, there is a likelihood that, depending on the damping torque amplification or the frequency of the damping control, errors may be generated in a zero power control which balances the input power and the output power in the power storage unit which stores the power for driving the drive motor, causing overcharge or overdischarge in the power storage unit. Conventionally, in order to avoid such overcharge or overdischarge in the power storage unit, control such as stopping the damping control by the drive motor after a prescribed time has been performed. However, there is a problem in that after stopping the damping control, due to the noise and the vibration caused by the engine torque vibration, marketability is impaired.